Surgical stapling device with lockout mechanism

ABSTRACT

A tool assembly includes a cartridge assembly and an anvil assembly pivotally secured to the cartridge assembly and movable between open and clamped positions. The cartridge assembly includes a channel member, a staple cartridge supported in the channel member, and an actuation sled positioned within the staple cartridge. The actuation sled is movable from a first position to a second position to eject staples from the staple cartridge. The tool assembly further includes a drive assembly having a clamping member movable from an initial position to an advanced position to move the actuation sled from the first position to the second position, and a lockout member secured to the channel member and moveable between a relaxed condition and a flexed condition. Movement of the actuation sled from the first position towards the second position causes the lockout member to move to the flexed condition to permit advancement of the drive assembly.

FIELD

This disclosure relates to surgical stapling devices having (fixed)single-use or replaceable cartridge assemblies. More particularly, thisdisclosure relates to a surgical stapling device having a lockoutmechanism for preventing firing of the surgical stapling device in theabsence of an actuating sled, cartridge assembly or in the presence ofspent cartridge assembly.

BACKGROUND

Surgical devices for stapling tissue are well known in the art andtypically include a handle assembly, a body portion extending distallyfrom the handle assembly, and a tool assembly supported on a distal endof the body portion. The tool assembly includes first and second jawswhich are movable in relation to each other between open and clamped orapproximated positions. The first jaw includes an anvil assembly and thesecond jaw supports a staple cartridge which houses a plurality ofstaples.

In known surgical stapling devices, a clamping member engages the firstand second jaws to move the first and second jaws from the open positionto the clamped position and is movable along the first and second jawsto advance an actuation sled to sequentially eject staples from thestaple cartridge. In the absence of a staple cartridge, or in thepresence of a spent staple cartridge, i.e., if the actuation sled ismissing, or in an advanced position, advancement of the clamping memberwill cause cutting of tissue without stapling tissue, resulting incomplications.

A continuing need exists in the art for a surgical stapling device witha lockout mechanism for preventing undesired advancement of the driveassembly when the actuating sled or staple cartridge is not present andwhen the staple cartridge is spent.

SUMMARY

A surgical stapling device includes an elongate body portion and a toolassembly pivotally secured to the elongate body portion. The toolassembly includes a cartridge assembly and an anvil assembly pivotallysecured to the cartridge assembly such that the tool assembly is movablebetween open and clamped positions. The cartridge assembly includes achannel member, a staple cartridge supported in the channel member, andan actuation sled positioned within the staple cartridge. The actuationsled is movable from a first position to a second position to ejectstaples from the staple cartridge. The tool assembly further includes adrive assembly having a clamping member movable from an initial positionto an advanced position to move the actuation sled from the firstposition to the second position, and a lockout member secured to thechannel member and moveable between a relaxed condition and a flexedcondition. Movement of the actuation sled from the first positiontowards the second position causes the lockout member to move to theflexed condition to permit advancement of the drive assembly.

In certain aspects of the disclosure, the lockout member is configuredto prevent advancement of the drive assembly when the actuation sled ismissing, or in the second position. The actuation sled may include aramp feature positioned to engage the lockout member as the actuationsled moves from the first position towards the second position. Thelockout member may include an interlock spring secured to the channelmember. The interlock spring may include a blocking portion that islocated in a first position adjacent the channel member when the lockingmechanism is in the relaxed condition and in a second position spacedfrom the channel member when the locking mechanism is in the flexedcondition. The interlock spring may be welded to the channel member. Theinterlock spring may include an engagement portion extending distallyfrom the blocking portion of the interlock spring.

In other aspects of the disclosure, the clamping member includes avertical strut, an upper beam, and a lower beam. The vertical strut mayinclude a knife. The clamping member may include a retraction ramp thatis engaged by the engagement portion of the interlock spring when thedrive assembly moves from the advanced position back to the initialposition. Engagement of the engagement portion of the interlock springby the retraction ramp of the clamping member may cause the interlockspring to move from the relaxed condition to the flexed condition.

A tool assembly includes a cartridge assembly and an anvil assemblypivotally secured to the cartridge assembly and movable in relation tothe cartridge assembly between open and clamped positions. The cartridgeassembly includes a channel member, a staple cartridge supported in thechannel member, and an actuation sled positioned within the staplecartridge. The actuation sled is movable from a first position to asecond position to eject staples from the staple cartridge. The toolassembly further includes a drive assembly having a clamping membermovable from an initial position to an advanced position to move theactuation sled from the first position to the second position, and alockout member secured to the channel member and moveable between arelaxed condition and a flexed condition. Movement of the actuation sledfrom the first position towards the second position causes the lockoutmember to move from the relaxed condition to the flexed condition topermit advancement of the drive assembly.

In certain aspects of the disclosure, the lockout member is configuredto prevent advancement of the drive assembly when the actuation sled ismissing, or in the second position. The actuation sled may include aramp feature positioned to engage the lockout member as the actuationsled moves from the first position towards the second position. Thelockout member may include an interlock spring secured to the channelmember. The interlock spring may include a blocking portion that islocated in a first position adjacent the channel member when the lockingmechanism is in the relaxed condition and in a second position spacedfrom the channel member when the locking mechanism is in the flexedcondition. The interlock spring may be welded to the channel member. Theinterlock spring may include an engagement portion extending distallyfrom the blocking portion of the interlock spring.

In other aspects of the disclosure, the clamping member includes avertical strut, an upper beam, and a lower beam. The vertical strut mayinclude a knife. The clamping member may include a retraction ramp thatis engaged by the engagement portion of the interlock spring when thedrive assembly moves from the advanced position back to the initialposition. Engagement of the engagement portion of the interlock springby the retraction ramp of the clamping member may cause the interlockspring to move from the relaxed condition to the flexed condition.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of the disclosure are described herein with reference tothe drawings, wherein:

FIG. 1 is a side, perspective view of a powered surgical stapling deviceincluding a loading unit according to aspects of the disclosure having atool assembly in an open position;

FIG. 2 is a bottom, perspective view of the loading unit shown in FIG.1;

FIG. 3 is side perspective view with parts separated of the loading unitshown in FIGS. 1 and 2;

FIG. 4 is an enlarged view of an actuation sled indicated in the area ofdetail shown in FIG. 3;

FIG. 5 is a bottom, perspective view of the actuation sled shown in FIG.4;

FIG. 6 is an enlarged view of an interlock spring indicated in the areaof detail shown in FIG. 3;

FIG. 7 is a top, perspective view of a channel member of the loadingunit shown in FIG. 2 and the interlock spring shown in FIG. 6 with partsseparated;

FIG. 8 is a top, perspective view of a proximal portion of the channelmember and the interlock spring shown in FIG. 7 assembled;

FIG. 9 is a side, perspective view of a clamping member indicated in thearea of detail shown in FIG. 3;

FIG. 10 is a bottom, perspective view from the distal end of theclamping member shown in FIG. 9;

FIG. 11 is a bottom, perspective view from the proximal end of theclamping member shown in FIGS. 9 and 10;

FIG. 12 is an enlarged view of the indicated area of detail shown inFIG. 2;

FIG. 13 is a cross-sectional view taken along section line 13-13 shownin FIG. 1 with the tool assembly in the open position;

FIG. 14 is an enlarged view of the indicated area of detail shown inFIG. 13;

FIG. 15 is a bottom, perspective view of a tool assembly of the loadingunit shown in FIG. 2 with the tool assembly in a clamped position andthe drive assembly in a partially advanced position;

FIG. 16 is an enlarged view of the indicated area of detail shown inFIG. 15;

FIG. 17 is a cross-sectional view taken along section line 17-17 shownin FIG. 16;

FIG. 18 is the bottom, perspective view shown in FIG. 16 with the driveassembly in a further partially advanced position;

FIG. 19 is a cross-sectional view taken along section line 19-19 shownin FIG. 18;

FIG. 20 is the cross-sectional view shown in FIG. 13 with the actuationsled in a fully advanced position and the drive assembly in a partiallyretracted position;

FIG. 21 is an enlarged view of the indicated area of detail shown inFIG. 20;

FIG. 22 is the side, cross-sectional view shown in FIG. 17 with thedrive assembly in a partially retracted position and the interlockspring in a flexed condition;

FIG. 23 is the side, cross-sectional view shown in FIG. 22 with thedrive assembly in a further partially retracted position and theinterlock spring in an initial or unflexed condition;

FIG. 24 is the side, cross-sectional view shown in FIG. 23 with aclamping member of the drive assembly inverted relative to the toolassembly and in the partially advanced position; and

FIG. 25 is the side, cross-sectional view shown in FIG. 24 with thedrive assembly in a further partially advanced position.

DETAILED DESCRIPTION

The disclosed surgical stapling device will now be described in detailwith reference to the drawings in which like reference numeralsdesignate identical or corresponding elements in each of the severalviews. However, it is to be understood that the aspects of thedisclosure are merely exemplary of the disclosure and may be embodied invarious forms. Well-known functions or constructions are not describedin detail to avoid obscuring the disclosure in unnecessary detail.Therefore, specific structural and functional details disclosed hereinare not to be interpreted as limiting, but merely as a basis for theclaims and as a representative basis for teaching one skilled in the artto variously employ the disclosure in virtually any appropriatelydetailed structure. In addition, directional terms such as front, rear,upper, lower, top, bottom, distal, proximal, and similar terms are usedto assist in understanding the description and are not intended to limitthe disclosure.

In this description, the term “proximal” is used generally to refer tothat portion of the device that is closer to a clinician, while the term“distal” is used generally to refer to that portion of the device thatis farther from the clinician. In addition, the term “clinician” is usedgenerally to refer to medical personnel including doctors, nurses, andsupport personnel.

The disclosed surgical stapling device includes a lockout mechanism forpreventing advancement of a drive assembly in the absence of anactuating sled, cartridge assembly and/or in the presence of apreviously fired or defective cartridge assembly.

FIG. 1 illustrates a surgical stapling device according to exemplaryaspects of the disclosure shown generally as stapling device 10. Thestapling device 10 includes a powered handle assembly 20, an adapterassembly 30 releasably secured to the powered handle assembly 20, and aloading unit 100 releasably secured to the adapter assembly 30. Thehandle assembly 20 include a stationary grip 22 that supports actuationbuttons 24 a, 24 b for controlling operation of various functions of thestapling device 10 including clamping and cutting of tissue. Althoughshown as individual or separable components, it is envisioned that anyor all of the powered handle assembly 20, adapter assembly 30, andloading unit 100 may be integrally formed.

The stapling device 10 is illustrated as an electrically poweredstapling device including an electrically powered handle assembly thatmay support one or more batteries (not shown). Examples of electricallypowered stapling devices can be found in U.S. Pat. Nos. 9,055,943 and9,023,014. Alternately, it is envisioned that the loading unit 100 couldalso be incorporated into a manual stapling device such as disclosed inU.S. Pat. No. 6,238,908 or a stapling device that is configured for usewith a robotic system such as disclosed in U.S. Pat. No. 9,962,159 thatdoes not include a handle assembly.

FIG. 2 illustrates the loading unit 100 of the stapling device 10(FIG. 1) including a body portion 102 and a tool assembly 104 pivotallysecured to the body portion 102. A proximal end of the body portion 102is configured for releasable engagement with the adapter assembly 30(FIG. 1).

FIG. 3 illustrates the tool assembly 104 of the loading unit 100including a jaw assembly 106 having an anvil assembly 114 and acartridge assembly 116. The cartridge assembly 116 includes a staplecartridge 116 a and a channel member 118 configured to receive thestaple cartridge 116 a. In certain aspects of the disclosure, and asshown, the staple cartridge 116 a may be replaceable. The anvil assembly114 and cartridge assembly 116 are pivotable relative to each otherbetween an open position (FIG. 2) and an approximated or clampedposition (FIG. 15). The anvil assembly 114 and the cartridge assembly116 may be biased to the open position by one or more springs, e.g.,leaf springs 180. The loading unit 100 is substantially as described inU.S. Pat. No. 9,016,539 (“the '539 patent”). Accordingly, the componentsof the loading unit 100 which are common to that which is disclosed inthe '539 patent will only be described herein to the extent necessary tofully disclose the aspects of the lockout mechanism 140 and its methodof operation.

A drive assembly 120 extends through and from the body portion 102(FIG. 1) of the loading unit 100 into the tool assembly 104. The driveassembly 120 includes a dynamic clamping member 122 and a drive beam 124extending proximally from the dynamic clamping member 122 into the bodyportion 102 of the loading unit 100. In certain aspects of thedisclosure, the drive beam 124 of the drive assembly 120 is formed froma plurality of stacked sheets that are formed of a resilient or flexiblematerial, e.g., stainless steel. A proximal end of the drive beam 124 isconfigured to engage a drive member (not shown) of the adapter assembly30 (FIG. 1) and/or the powered handle assembly 20 (FIG. 1) for advancingand retracting the drive assembly 120 within the body portion 102 andthe tool assembly 104.

The anvil assembly 114 of the jaw assembly 106 of the tool assembly 104defines a longitudinal slot 151 (FIG. 13) and an inner clamping surface114 a on either side of the longitudinal slot 151. In certain aspects ofthe disclosure, the anvil assembly 114 includes an anvil body 150 and ananvil plate 152 (FIG. 13) secured to the underside of the anvil body 150to form the longitudinal slot 151. The anvil plate 152 defines aplurality of staple receiving depressions (not shown).

The channel member 118 of the cartridge assembly 116 is pivotallysecured to the anvil assembly 114. The channel member 118 defines achannel 119 that receives the cartridge assembly 116. The staplecartridge 116 a of the cartridge assembly 116 of the jaw assembly 106includes a cartridge body 156 supported in a cartridge holder 158, aplurality of staples “S”, and a staple firing assembly 160. Thecartridge body 156 of the staple cartridge 116 a is secured within thechannel 119 of the channel member 118 with, e.g., a snap-fit connection.Other forms of connections are contemplated and may be used in place ofthe snap-fit connection, or in addition thereto, to fixedly orreleasably secure the staple cartridge 116 a within the channel 119 ofthe channel member 118. The channel member 118 further defines alongitudinal slot 161 and a clamping surface 118 a on either side of thelongitudinal slot 161.

The cartridge body 156 of the staple cartridge 116 a defines a pluralityof laterally spaced staple retention slots 153 which are positioned inalignment with the staple receiving depressions (not shown) in the anvilplate 152 (FIG. 13) of the anvil assembly 114 when the tool assembly isin the clamped position. Each retention slot 153 receives a fastener orstaple “S” and a pusher 164. The staple firing assembly 160 includes anactuation sled 162 (FIG. 3) and a plurality of pusher members 164. Theactuation sled 162 is positioned within the cartridge body 156 of thestaple cartridge 116 a and is configured to pass longitudinally throughthe cartridge body 156 into engagement with the pushers 164 to lift thepushers within the cartridge body 156 to sequentially eject the staples“S” from the cartridge body 156.

FIGS. 4 and 5 illustrate the actuation sled 162 of the staple firingassembly 160 which includes a base portion 170, a central rib portion172 extending upwardly from the base portion 170, and first and secondpaired camming rib portions 174 a, 174 b. A ramp feature 176 extendsdownwardly from the base portion 170 and includes an angled surface 176a. The angle surface 176 a faces distally, i.e., away from the driveassembly 120. The ramp feature 176 may include a stop surface (notshown) for engaging a hard stop 118 b (FIG. 20) of the channel member118.

FIG. 6 illustrates an interlock spring 142 of the lockout mechanism 140.The interlock spring 142 includes a pair of tang portions 144, anelongate body or spring portion 146 extending from the each of tangportions 144, and a blocking portion 148 extending between the elongatebody portions 146. The tang portions 144 of the interlock spring 142 arespaced apart from one another to define a channel 145 through which thedynamic clamping member 122 (FIG. 3) of the drive assembly 120 (FIG. 3)may pass. An engagement portion 150 extends distally from the blockingportion 148. The blocking portion 148 of the interlock spring 142defines a notch or camming feature 149.

FIGS. 7 and 8 illustrate placement of the interlock spring 142 of thelockout mechanism 140 on the channel member 118 of the cartridgeassembly 116 of the loading unit 100. The channel member 118 defines acutout 117 for receiving the interlock spring 142. The cutout 117 isformed on an underside of a proximal portion of the channel member 118.Each of the tang portions 144 is secured to the channel member 118 oneither side of the longitudinal slot 161. In certain aspects of thedisclosure, the tang portions 144 are welded to the channel member 118.Alternatively, the tang portions 144 may be secured to the channelmember 118 in any suitable manner, including, with adhesives, mechanicalfasteners, or friction fit. The interlock spring 142 is positioned onthe channel member 118 such that the elongate body portions 146 of theinterlock spring 142 extend distally along the channel member 118 onopposite sides of the longitudinal slot 161. When the interlock spring142 is secured to the channel member 118, the blocking portion 148 ofthe interlock spring 142 extends across the longitudinal slot 161 suchthat the notch or camming feature 149 is centered in the blockingportion 148 of the locking spring 142 and is aligned with thelongitudinal slot 161 and the engagement portion extends along thelongitudinal slot 161. With only the tang portions 144 of the interlockspring 142 secured to the channel member 118, the elongate body portions146 of the interlock spring 142 are able to flex outwardly away from thechannel member 118.

FIGS. 9-11 illustrate the dynamic clamping member 122 of the driveassembly 120 which includes an upper flange portion 132, a lower flangeportion 134, and a vertical strut 136 interconnecting the upper flangeportion 132 and the lower flange portion 134. The upper flange portion132 is sized and dimensioned to be slidably received within thelongitudinal slot 151 (FIG. 13) of the anvil assembly 114 and includes aclamping surface 132 a (FIG. 10) that engages the inner clamping surface114 a (FIG. 13) of the anvil assembly 114 to cause the pivoting of theanvil assembly 114 relative to the cartridge assembly 116 to move thetool assembly 104 from the open position to the clamped position. Thelower flange portion 134 is sized and dimensioned to be slidablyreceived along an outer surface of the channel member 118 (FIG. 15) andincludes clamping surfaces 134 a (FIG. 9) facing the upper flangeportion 132 of the dynamic clamping member 122. The vertical strut 136of the dynamic clamping member 122 is received within the longitudinalslot 161 of the channel member 118 and includes a knife 136 a.

The dynamic clamping member 122 of the drive assembly 120 defines aretraction ramp 133 (FIG. 11) on a proximal portion of the lower flangeportion 134. The retraction ramp 133 is positioned to be aligned withthe engagement portion 150 (FIG. 12) of the interlock spring 142. Thelower flange portion 134 of the dynamic clamping member 122 includes alead-in surface 137 (FIG. 11) and the upper flange portion 132 of thedynamic clamping member 122 includes a lead-in surface 139 (FIG. 9). Aswill be described in further detail below, the lead-in surface 137 ofthe lower flange portion 134 includes an angled surface 137 a and ablocking surface 137 b, and the lead-in surface 139 of the upper flangeportion 132 includes a blocking surface 139 a.

FIGS. 12-14 illustrate the loading unit 100 of the stapling device 10(FIG. 1) including the staple cartridge 116 a in a pre-fired conditionand the drive assembly 120 in a retracted position. In the pre-firedcondition, the actuation sled 162 of the cartridge assembly 116 is in aninitial position in which the ramp feature 176 of the actuation sled 162is positioned proximal of the blocking portion 148 of the interlockspring 142, resulting in the interlock spring 142 being in an unflexedcondition. When the drive assembly 120 is in the retracted position, thedynamic clamping member 122 of the drive assembly 120 is longitudinallyspaced from the cartridge assembly 116 of the jaw assembly 106. Springs180 bias the anvil assembly 114 and the cartridge assembly 116 to theopen position to permit placement of tissue between tissue contactingsurfaces 114 b (FIG. 13), 116 b of the respective anvil assembly 114 andcartridge assembly 116. In the retracted position, the dynamic clampingmember 122 of the drive assembly 120 is also longitudinally spaced fromthe actuation sled 162.

FIGS. 15 and 16 illustrate the drive assembly 120 of the loading unit100 in a first partially advanced position. Movement of the driveassembly 120 to the first partially advanced position, as indicated byarrow “A” in FIG. 16, pivots the jaw assembly 106 to the clampedposition, as indicated by arrow “B” in FIG. 15. More particularly, theupper flange portion 132 of the dynamic clamping member 122 engages theclamping surface 114 a of the anvil assembly 114 and the lower flangeportion 134 of the dynamic clamping member 122 engages the clampingsurface 118 a of the channel member 118 to pivot the channel member 118,including the staple cartridge 116 a, to the clamped position. In thefirst partially advanced position, the dynamic clamping member 122 ofthe drive assembly 120 may be, as shown, longitudinally spaced from theactuation sled 162 to prevent any unintended advancement of theactuation sled 162 during closing of the jaw assembly 106.

FIG. 17 illustrates the drive assembly 120 of the loading unit 100 in asecond partially advanced position. Movement of the drive assembly 120to the second partially advanced position, as indicated by arrows “C”,causes the dynamic clamping member 122 to engage the actuation sled 162to cause advancement of the actuation sled 162. Advancement of theactuation sled 162 causes the ramp feature 176 of the actuation sled 162to engage the blocking portion 148 of the interlock spring 142 at thenotch or camming feature 149.

FIGS. 18 and 19 illustrate continued advancement of the drive assembly120 of the loading unit 100, as indicated by arrows “D”, to a thirdpartially advanced position. The continued advancement of the driveassembly 120 to the third partially advanced position causes thecontinued advancement of the actuation sled 162 in relation to theinterlock spring 142. As the actuation sled 142 moves distally inrelation to the interlock spring 142, the ramp feature 176 of theactuation sled 162 moves beneath the blocking portion 148 to flex theelongate portions of the interlock spring 142 such that the blockingportion 148 of the interlock spring 142 lifts in the direction of arrow“E” in FIG. 19 over the ramp feature 176 and position the blockingportion 148 onto the angled surface 137 a of the lead-in surface 137 ofthe lower flange portion 134 of the dynamic clamping member 122. As theblocking portion 148 of the interlock spring 142 flexes away from thechannel member 118, the lower flange portion 134 of the dynamic clampingmember 122 can clear the blocking portion 148, thereby permittingcontinued advancement of the drive assembly 120.

FIGS. 20 and 21 illustrate the jaw assembly 106 of the loading unit 100following an actuation stroke of the stapling device 10 (FIG. 1). Theactuation sled 162 of cartridge assembly 116 is in its distal-mostposition following the actuation stroke of the loading unit 100 andremains in the distal-most position during retraction of the driveassembly 120. The drive assembly 120 is retracted, as indicated by arrow“F” in FIG. 20, to a first retracted position wherein the dynamicclamping member 122 engages the interlock spring 142. More particularly,the engagement portion 150 of the interlock spring 142 engages the lowerflange portion 134 at the retraction ramp 133. Engagement of theengagement portion 150 of the interlock spring 142 with the retractionramp 133 causes the blocking portion 148 of the interlock spring 142 toflex away from the channel portion 118, as indicated by arrow “G” inFIG. 21, such that the lower flange portion 134 of the dynamic clampingmember 122 can pass over and clear the blocking portion 148, therebypermitting continued retraction of the drive assembly.

FIG. 22 illustrates the continued retraction of the drive assembly 120.More particularly, once the blocking portion 148 of the interlock spring142 passes the retraction ramp 133 of the dynamic clamping member 122,the blocking portion 148 of the interlock spring 142 remains inengagement with an outer surface of the lower flange portion 134 of thedynamic clamping member 122 to permit the dynamic clamping member 122 topass by the blocking portion 148 of the interlock spring 142, permittingcontinued retraction of the drive assembly 120 to a position in whichlower beam 134 of the dynamic clamping member 122 is positionedproximally of the blocking portion 148.

FIG. 23 illustrates the drive assembly 120 in a locked position.Following a stapling procedure, the drive assembly 120 is retracted to apoint in which the lower beam 134 is positioned proximally of theblocking portion 148 of the interlock spring 142. Once the lower beam134 is positioned proximally of the blocking portion 148 of theinterlock spring 142, the drive assembly 120 is prevented from beingreadvanced. More particularly, in the absence of the actuation sled 162(FIG. 19), i.e., without the flexing of the interlock spring 142 causedby the ramp feature 176 of the actuation sled 162, the blocking portion148 of the interlock spring 142 engages the blocking surface 137 b ofthe lead-in surface 137 of the lower flange portion 134 of the dynamicclamping member 122. Engagement of the blocking surface 137 b of thelower flange portion 134 of the dynamic clamping member 122 preventscontinued advancement of the drive assembly 120 past the blockingportion 148 of the interlock spring 142.

FIG. 24 illustrates the drive assembly 120 within the jaw assembly 104of the loading unit 100 in an inverted or upside-down condition. Thedrive assembly 120 is in the inverted condition as a result of amanufacturing error in which the dynamic clamping member 122 ispositioned one hundred-eighty degrees (180°) from its correct position.In this manner, the knife 136 a is not aligned with the gap definedbetween the tissue contacting surfaces 114 b (FIG. 13), 116 b of theanvil and cartridge assemblies 114, 116, respectively. Firing of theloading unit 100 when the drive assembly 120 is in the inverted positionmay cause significant damage to tissue being stapled (not shown) as theknife 136 a of the dynamic clamping member 122 is not in properalignment with the jaw assembly 106.

FIG. 25 illustrates partial advancement of the drive assembly 120, asindicated by arrow “H”, when the drive assembly 120 is in the invertedcondition. The partial advancement of the drive assembly 120 causesadvancement of the actuation sled 162 which cause partial flexing of theinterlock spring 142, as indicated by arrow “I”. However, since thedynamic clamping member 122 is inverted, the blocking portion 148 of theinterlock spring 142 engages the blocking surface 139 a of the lead-insurface 139 of the upper flange portion 132 of the dynamic clampingmember 122 instead of the angled surface 137 a of the lead-in surface137 of the lower flange portion 134 of the dynamic clamping member 122.In this manner, even in the presence of the actuation sled 162, theinterlock spring 142 prevents further advancement of the drive assembly120 when the dynamic clamping member 122 of the drive assembly isimproperly installed in the stapling device 10.

Persons skilled in the art will understand that the devices and methodsspecifically described herein and illustrated in the accompanyingdrawings are non-limiting exemplary aspects. It is envisioned that theelements and features illustrated or described in connection with theexemplary aspects may be combined with the elements and features ofanother without departing from the scope of the disclosure. As well, oneskilled in the art will appreciate further features and advantages ofthe disclosure based on the above-described aspects. Accordingly, thedisclosure is not to be limited by what has been particularly shown anddescribed, except as indicated by the appended claims.

1. A surgical stapling device comprising: an elongate body portion; anda tool assembly pivotally secured to the elongate body portion, the toolassembly including, a cartridge assembly including a channel member, astaple cartridge supported in the channel member, and an actuation sledpositioned within the staple cartridge, the actuation sled being movablefrom a first position to a second position to eject staples from thestaple cartridge the channel member including an underside; an anvilassembly pivotally secured to the cartridge assembly such that the toolassembly is movable between open and clamped positions; a drive assemblyincluding a clamping member movable from an initial position to anadvanced position to move the actuation sled from the first position tothe second position; and a lockout member secured to the underside ofthe channel member and moveable between relaxed and flexed conditions,wherein movement of the actuation sled from the first position towardsthe second position causes the lockout member to move to the flexedcondition to permit advancement of the drive assembly.
 2. The surgicalstapling device of claim 1, wherein the lockout member is configured toprevent advancement of the drive assembly when the actuation sled is inthe second position.
 3. The surgical stapling device of claim 1, whereinthe actuation sled includes a ramp feature positioned to engage thelockout member as the actuation sled moves from the first positiontowards the second position.
 4. The surgical stapling device of claim 1,wherein the lockout member includes an interlock spring secured to thechannel member.
 5. The surgical stapling device of claim 4, wherein theinterlock spring includes a blocking portion that is located in a firstposition adjacent the channel member when the locking mechanism is inthe relaxed condition and in a second position spaced from the channelmember when the locking mechanism is in the flexed condition.
 6. Thesurgical stapling device of claim 4, wherein the interlock spring iswelded to the channel member.
 7. The surgical stapling device of claim1, wherein the clamping member includes a vertical strut, an upper beam,and a lower beam, and the vertical strut includes a knife.
 8. Thesurgical stapling device of claim 4, wherein the interlock springincludes an engagement portion extending distally from the blockingportion of the interlock spring.
 9. The surgical stapling device ofclaim 8, wherein the clamping member includes a retraction ramp that isengaged by the engagement portion of the interlock spring when the driveassembly moves from the advanced position back to the initial position.10. The surgical stapling device of claim 9, wherein engagement of theengagement portion of the interlock spring with the retraction ramp ofthe clamping member causes the interlock spring to move from the relaxedcondition to the flexed condition.
 11. A tool assembly comprising: acartridge assembly including a channel member, a staple cartridgesupported in the channel member, and an actuation sled positioned withinthe staple cartridge, the actuation sled being movable from a firstposition to a second position to eject staples from the staplecartridge, the channel member including an underside; an anvil assemblypivotally secured to the cartridge assembly and movable in relation tothe cartridge assembly between open and clamped positions; a driveassembly including a clamping member movable from an initial position toan advanced position to move the actuation sled from the first positionto the second position; and a lockout member secured to the underside ofthe channel member and moveable between relaxed and flexed conditions,wherein movement of the actuation sled from the first position towardsthe second position causes the lockout member to move from the relaxedcondition to the flexed condition to permit advancement of the driveassembly.
 12. The tool assembly of claim 11, wherein the lockout memberis configured to prevent advancement of the drive assembly when theactuation sled is in the second position.
 13. The tool assembly of claim11, wherein the actuation sled includes a ramp feature positioned toengage the lockout member as the actuation sled moves from the firstposition towards the second position.
 14. The tool assembly of claim 11,wherein the lockout member includes an interlock spring secured to thechannel member.
 15. The tool assembly of claim 14, wherein the interlockspring includes a blocking portion that is located in a first positionadjacent the channel member when the locking mechanism is in the relaxedcondition and in a second position spaced from the channel member whenthe locking mechanism is in the flexed condition.
 16. The tool assemblyof claim 14, wherein the interlock spring is welded to the channelmember.
 17. The tool assembly of claim 11, wherein the clamping memberincludes a vertical strut, an upper beam, and a lower beam, and thevertical strut includes a knife.
 18. The tool assembly of claim 14,wherein the interlock spring includes an engagement portion extendingdistally from the blocking portion of the interlock spring.
 19. The toolassembly of claim 18, wherein the clamping member includes a retractionramp that is engaged by the engagement portion of the interlock springwhen the drive assembly moves from the advanced position back to theinitial position.
 20. The tool assembly of claim 19, wherein engagementof the engagement portion of the interlock spring with the retractionramp of the clamping member causes the interlock spring to move from therelaxed condition to the flexed condition.